Effect of Singlet Oxygen on the Stomatal and Cell Wall of Rice Seedling Under Different Stresses

Singlet oxygen (¹O₂), a reactive oxygen species, can oxidize lipids, proteins, and DNA at high concentrations, leading to cell death. Despite its extremely short half-life (10^-5 s), ¹O₂ acts as a critical signaling molecule, triggering a retrograde pathway from chloroplasts to the nucleus to regulate nuclear gene expression. In this study, rice seeds were treated with 0, 5, 20 and 80 μM Rose Bengal (RB, a photosensitizer) under moderate light for 3 days to induce ¹O₂ generation. Treatment with 20 μM RB reduced stomatal density by approximately 25% in three-leaf-stage rice seedlings, while increasing the contents of pectin, hemicellulose, and cellulose in root cell walls by 30-40%. Under drought, salinity, or shading stress, 20 μM RB treatment significantly improved rice tolerance, as evidenced by higher relative water contents (49-58%) and chlorophyll contents (60-76%) and lower malondialdehyde (37-43%) and electrolyte leakage (29-37%) compared to the control. Moreover, RT-qPCR analysis revealed that the significant up-regulation of stomatal development genes (<i>OsTMM</i> and <i>OsβCA1</i>) and cell wall biosynthesis genes (<i>OsF8H</i> and <i>OsLRX2</i>) was associated with RB-induced ¹O₂ production. Thus, under controlled environmental conditions, ¹O₂ may regulate stomatal development and cell wall remodeling to enhance rice tolerance to multiple abiotic stresses. These results provide new perspectives for the improvement of rice stress tolerance.